1. Field of the Invention
The present invention relates to an electrical switching apparatus operating mechanism and, more specifically to a decoupling assembly disposed between the charging assembly motor and the charging assembly cam shaft structured to decouple the charging assembly motor and the charging assembly cam shaft in the event the charging motor fails to stop rotating.
2. Background Information
An electrical switching apparatus, typically, includes a housing, at least one bus assembly having a pair of contacts, a trip device, and an operating mechanism. The housing assembly is structured to insulate and enclose the other components. The at least one pair of contacts include a fixed contact and a movable contact and typically include multiple pairs of fixed and movable contacts. Each contact is coupled to, and in electrical communication with, a conductive bus that is further coupled to, and in electrical communication with, a line or a load. A trip device is structured to detect an over current condition and to actuate the operating mechanism. An operating mechanism is structured to both open the contacts, either manually or following actuation by the trip device, and close the contacts.
That is, the operating mechanism includes both a closing assembly and an opening assembly, which may have common elements, that are structured to move the movable contact between a first, open position, wherein the contacts are separated, and a second, closed position, wherein the contacts are coupled and in electrical communication. The operating mechanism includes a rotatable pole shaft that is coupled to the movable contact and structured to move each movable contact between the closed position and the open position. Elements of both the closing assembly and the opening assembly are coupled to the pole shaft so as to effect the closing and opening of the contacts.
An electrical switching apparatus typically had a stored energy device, such as at least one opening spring, and at least one link coupled to the pole shaft. The at least one link, typically, included two links that acted cooperatively as a toggle assembly. When the contacts were open, the toggle assembly was in a first, collapsed configuration and, conversely, when the contacts were closed, the toggle assembly was, typically, in a second, toggle position or in a slightly over-toggle position. The spring biased the toggle assembly to the collapsed position. The spring and toggle assembly were maintained in the second, toggle position by the trip device.
The trip device included an over-current sensor, a latch assembly and may have included one or more additional links that were coupled to the toggle assembly. Alternately, the latch assembly was directly coupled to the toggle assembly. When an over-current situation occurred, the latch assembly was released allowing the opening spring to cause the toggle assembly to collapse. When the toggle assembly collapsed, the toggle assembly link coupled to the pole shaft caused the pole shaft to rotate and thereby move the movable contacts into the open position.
Typically, the force required to close the contacts was, and is, greater than what a human may apply. As such, the operating mechanism typically included a mechanical closing assembly to close the contacts. The closing assembly, typically, included at least one stored energy device, such as a spring, and/or a motor. A common configuration included a motor that compressed one or more springs in the closing assembly. That is, the closing springs were coupled to a cam roller that engaged a cam coupled to the motor. As the motor rotated the cam, the closing springs were compressed or charged. The closing springs were maintained in the compressed configuration by a latch assembly. The latch assembly was actuated by a user to initiate a closing procedure. The closing assembly is structured to apply the energy stored in the springs to the toggle assembly so as to cause the pole shaft to rotate and close the contacts.
In many electrical switching apparatuses the springs are coupled to the toggle assembly via a cam roller. That is, the toggle assembly also included a cam roller, typically at the toggle joint. The closing assembly further included one or more cams disposed on a common cam shaft with the closing spring cam. Alternatively, depending upon the configuration of the cam, both the closing spring cam roller and the toggle assembly cam roller could engage the same cam. When the closing springs were released, the closing spring cam roller applied force to the associated cam and caused the cam shaft to rotate. Rotation of the cam shaft would also cause the cam associated with the toggle assembly cam roller to rotate. As the cam associated with the toggle assembly cam roller rotated, the cam caused the toggle assembly cam roller, and therefore the toggle assembly, to be moved into selected positions and/or configurations. Alternatively, as set forth in U.S. patent application Ser. No. 11/693,159, which is incorporated by reference, the springs could be coupled to a ram assembly having a ram body that moved over a predetermined path. The ram body was structured to directly engage the toggle assembly and move the toggle assembly into a selected position. That is, whether the closing assembly utilized a cam or a ram assembly, the toggle assembly was moved so as to rotate the pole shaft into a position wherein the contacts were closed.
For example, during a closing procedure the toggle assembly would initially be collapsed and, therefore, the contacts were open. When the closing springs were released, the rotation of the cam associated with the toggle assembly cam roller would cause the toggle assembly to move back into the second, toggle position, thereby closing the contacts. This motion would also charge the opening springs. Simultaneously, or near simultaneously, the trip device latch would be reset thereby holding the toggle assembly in the second, toggle position. After the contacts were closed, it was common to recharge the closing spring so that, following an over current trip, the contacts could be rapidly closed again. That is, if the closing springs were charged, the contacts could be closed almost immediately without having to wait to charge the closing springs.
As noted above, the charging of the closing springs was typically accomplished via a motor. The motor had an output shaft that was coupled, directly or indirectly, to the shaft of the charging cam. In addition to the charging motor, most electrical switching apparatuses included an elongated manual charging handle. The charging handle also acted upon the shaft of the charging cam either directly or indirectly.
As set forth in U.S. patent application Ser. No. 10/733,449, filed Apr. 10, 2007, entitled “OVER RUNNING CLUTCH FOR A DIRECT DRIVE MOTOR OPERATOR”, an over-running clutch assembly for an electrical switching apparatus is provided. The over running clutch assembly includes a sprocket and a hub assembly. The hub assembly is rotatably coupled to the sprocket and structured to rotate in a charging direction relative to the sprocket. The sprocket is fixed to a motor shaft. The hub assembly is structured to be disengagably fixed to a cam shaft in the charging assembly. A manual charging handle is also coupled to the cam shaft and is structured to rotate the cam shaft in a charging direction. In this configuration, an operator may charge the closing springs of the electrical switching apparatus using either the handle assembly or the motor. When the handle assembly is used to charge the closing springs, the cam shaft causes the hub assembly to rotate over the sprocket. Thus, the rotation of the cam shaft is not transferred to the motor. When the motor is used, the motor turns both the sprocket and the hub assembly. The hub assembly transfers the rotational force from the motor to the cam shaft.
The over-running clutch assembly, however, is not structured to allow the hub assembly to disengage from the sprocket in the event of a failure to disengage the motor. That is, the charging assembly as disclosed in U.S. patent application Ser. No. 10/733,449, filed Apr. 10, 2007, entitled “OVER RUNNING CLUTCH FOR A DIRECT DRIVE MOTOR OPERATOR”, as well as in U.S. patent application Ser. No. 11/693,159, which is incorporated by reference, provides for a latch assembly structured to latch the charging cam in a stop position when the closing springs are charged. Because the latch assembly locks the cam in place, at least until the latch assembly is released, any subsequent rotational force applied to the cam or the associated cam shaft is very likely to damage the electrical switching apparatus operating mechanism.
There is, therefore, a need for a decoupling assembly for a charging assembly for an electrical switching apparatus structured to decouple the charging motor and the charging assembly cam shaft.
There is a further need for a decoupling assembly for a charging assembly for an electrical switching apparatus that acts in concert with an over-running clutch assembly.